Internal combustion engines, including diesel engines, gasoline engines, gaseous fuel-powered engines, and other engines known in the art, produce exhaust gases having a complex mixture of air pollutants. These air pollutants are composed of gaseous compounds including, among other things, oxides of nitrogen (NOx). In order to comply with the regulation of NOX, some engines employ a strategy called selective catalytic reduction (SCR). The SCR is an exhaust treatment process where a reductant, most commonly urea or a water/urea solution, is selectively injected into the exhaust gas stream of an engine and adsorbed onto a downstream substrate. The injected urea solution decomposes into ammonia which decomposes NOX in the exhaust gas into less harmful components.
The exhaust systems of the internal combustion engines may also be equipped with noise attenuation devices, such as mufflers. These noise attenuation devices reduce the intensity of the exhaust noise generated during the operation of the internal combustion engine. The noise attenuation devices are configured to reduce the noise level in the immediate vicinity of the engine.
U.S. Pat. No. 5,578,277 discloses a catalytic converter and muffler. The catalytic converter and muffler may be used to purify exhaust from a relatively large diesel engine. The device includes various structural components that are mounted in the exhaust flow path within a housing having an inlet and an outlet.